The results from a study looking at interobserver variability in sizing of fenestrated and branched stent grafts have shown a high level of agreement between observer and also some critical discrepancies with may affect clinical results.
Hiroshi Banno, Department of Vascular Surgery, Henri Mondor Hospital, Créteil, France, presented the data at the European Society for Vascular Surgery (ESVS) annual meeting (18–21 September, Budapest, Hungary). He said that sizing subsequent to accurate measurements of preoperative CT scans are crucial for successful of fenestrated or branched endograft EVAR for complex aneurysms. Reports in the literature have shown high level of agreement between endovascular surgeons but less agreement between observers and manufacturers.
“Although there are several reports concerning interobserver variability on measurements for standard EVAR, little is known about measurements for complex aortic aneurysm which requires visceral branch preservation. Therefore we undertook the WINDOWS study,” he said.
The WINDOWS study was a French multicentre, prospective single-arm trial of fenestrated and branched EVAR for complex aortic aneurysm. In the trial, two independent observers reviewed all preoperative CT scans of 268 patients enrolled between September 2009 and October 2012. The observers looked at aortic diameter (thoracic, coeliac artery, superior mesenteric artery, lowest renal artery, infrarenal), eventual stenosis (>70%) of visceral branches, vessel position (coeliac, superior mesenteric and both renal arteries), extent of aneurysm, level of proximal landing zone and proximal device diameter.
In case of discrepancy between the two observers, a third observer provided the final decision as core laboratory. Those core laboratory data were compared with that obtained 1) by investigators in each centre (extent of aneurysm and aortic diameter at different levels), 2) from manufacturer (level of proximal landing zone, device diameter, and target vessel position), 3) with all data reviewed by the two observers.
The researchers assessed the reproducibility by Kappa statistics (values 0–0.20 as slight, 0.21 to 0.40 as fair, 0.41 to 0.60 as moderate, 0.61 to 0.80 as substantial and 0.81–1.00 as almost perfect agreement) for qualitative data and by both Bland-Altman plot and Passing-Bablok regression analysis for quantitative data.
For the extent of the aneurysm, the Kappa statistics showed almost perfect agreement between observers and investigator, “but there were cases with discrepancy.” For vessel orientation, the statistics showed substantial or almost perfect agreement between manufacturer and the observers, but there were also cases with discrepancy. The same happened for proximal landing zone and device diameter, with almost perfect agreement, but some discrepancy. Banno told delegates that these discrepancies could have been clinically significant.
In summary, he said, agreement for visceral artery stenosis and aortic diameter was moderate to almost perfect, for the extent of the aneurysm it was almost perfect, for visceral artery orientation agreement was substantial in one case and almost perfect for the others, for visceral artery distance it was excellent and for proximal landing zone and device diameter it was almost perfect.
“However, the discrepancies included ≥45mm (22.5°) in angle, ≥5mm in distance, proximal landing zone and ≥2 size in proximal device diameter. The correlation between these discrepancies and clinical results should be investigated,” he said.
Banno noted that this is the first large-scale analysis focused on interobserver variability of sizing for fenestrated and branched EVAR. “The measurement data showed statistically good agreement, but there were some critical discrepancy between observers that may influence clinical results. Surgeons should be careful in cases when there is sizing discrepancy compared with manufacturer,” he said.